Answer:
C. Yield to Call
Step-by-step explanation:
As the investor pays $125,000 for 10% having a face value of $100,000 so it seems that there is a premium of 25% in the bond. Now in the case when the bond is called before to the maturity that occurs when the market rate is less than the coupon rate. Also the same is shown in the question
So for determining the yield, the best way measure and appropriate is yield to call